OBD 2 Automotive Repair Strategies

Zusammenfassung

In the early part of the 21st century, we find our lives intertwined with a maze of technological wonders. From cell-phones to personal computers, no human being today can escape it. Automobiles are no exception to this rule.

With the ever changing emission laws of today, the one constant in the automotive industry is that things always change and will continue to do so. OBD II was designed from the beginning to do so as well. Late model vehicle systems are much more demanding, in both the amount of technology they posses and in the knowledge necessary to repair them. This work was designed to just that, a step-by step diagnostic approach to OBD II systems. It is also written with the State Inspections in mind. This is in direct response to the increasing adoption of OBD II inspections by most States throughout the country. OBD II repair don’t have to be difficult or cumbersome and knowledge is the key to successful OBD II diagnostics and repair.

- Basics of OBD II- What is OBD II?- Why do we need it? The Federal Test Procedure (FTP)- Technical aspects of OBD II. (FF, Monitors, Pending & Current Codes, The Drive Cycle, Re-setting Monitors, etc)- The data link connector- Diagnostic Trouble Code implementation- Resetting Monitors- What are Freeze Frames and how are they useful in diagnostics- A word about misfires- Do I need an OEM scanner or can I get by with an aftermarket scan tool?- Generic vs. Enhanced. What's the difference? why do you need to pull-out both codes?- The vehicle failed OBD II-State Inspection, but is passing a 5 gas emissions test. Why is it?- Resetting fuel trims. It’s not the same procedure for every system- The Diagnostic Executive or Task Manager. What is it?- Bi-Directional control capabilities are revolutionizing the diagnostic process- Diagnosing EVAP leaks. It doesn’t have to be complicated

Chapter 2

- Base-lining the system includes retrieving FF, codes, & monitor status- Freeze Frames information gathering- Monitor status flag- Code Setting Criteria. How and why was the code set?- Freeze Frame and Code Setting Criteria comparison- Dividing the diagnostic process into systems and using the codes to detect system faults- First rule of diagnostics—Know the system you’re working on- System by System outlook- Which Monitors are Incomplete. The need to prove each system without having to run a drive cycle by using the scanner, saving time & money- General Idle PID Snap-Shot

- Putting it all together.- Principles of diagnostics- Basic Scope Testing and Bi-Directional Control- No-Start, General Diagnostics- The correct decision making process to a sound repair- Don't assume anything or get caught in a particular mind set- Taking all the facts into account

Buchvorschau

OBD 2 Automotive Repair Strategies - Mandy Concepcion

purposes.

Preface

In the early part of the 21st century, we find our lives intertwined with a maze of technological wonders. From cell-phones to personal computers, no human being today can escape it. Automobiles are no exception to this rule.

With the ever changing emission laws of today, the one constant in the automotive industry is that things always change and will continue to do so. OBD II was designed from the beginning to do so as well. Late model vehicle systems are much more demanding, in both the amount of technology they posses and in the knowledge necessary to repair them. This work was designed to just that, a step-by step diagnostic approach to OBD II systems. It is also written with the State Inspections in mind. This is in direct response to the increasing adoption of OBD II inspections by most States throughout the country. OBD II repair don’t have to be difficult or cumbersome and knowledge is the key to successful OBD II diagnostics and repair.

About the author:

Mandy Concepcion has worked in the automotive field for over 21 years. He holds an Associates Degree in Applied Electronics Engineering as well as an ASE L1 certification. For the past 12 years he has been exclusively involved in the diagnosis of all the different electronic systems found in today’s vehicles. It is here where he draws extensive practical knowledge from his experience and hopes to convey it in this book.

- Dividing the diagnostic process into systems and using the codes to detect system faults

- First rule of diagnostics—Know the system you’re working on

- System by System outlook

- Which Monitors are Incomplete. The need to prove each system without having to run a drive cycle by using the scanner, saving time & money

- General Idle PID Snap-Shot

Chapter 3

- INTRODUCTION

- OBD-2 Generic PID list

- OBD I and OBD II, and general PID analysis

- FUEL DELIVERY FAULT DETECTION

- TEST # 1

- TEST #2

- TEST #3

- TEST #4

- TEST #5

- RUNNING THE MONITORS IN YOUR MIND USING THE SCANNER

Chapter 4

- Putting it all together.

- Principles of diagnostics

- Basic Scope Testing and Bi-Directional Control

- No-Start, General Diagnostics

- The correct decision making process to a sound repair

- Don't assume anything or get caught in a particular mind set

- Taking all the facts into account

Chapter-1

Basics of OBD-II

In this Chapter, we’ll take a look at the basics of OBD II. This Chapter is intended to prepare the technician for the rest of the book. However, it is not meant to be a comprehensive article of all there is to know about OBD II. What you’ll find here is strictly what you need to know to properly diagnose and repair any OBD II system. For in-depth legal information about OBD II there are simply plenty of publications out there that’ll satisfy any working tech. Enjoy your readings.

What is OBD II?

OBD I or on-board diagnostics first generation (pre 1996) was a primitive and rudimentary diagnostics system. It was a huge step forward at the time, but fell short when it came to the stringent emission laws of the mid 1990’s. OBD I was mainly a good-or-bad fault detection system and did not allow for the detection of deteriorated and older components. This older system was also proprietary in nature. In many cases, manufacturers would hide the DLC (Diagnostics Link Connector), which is used to connect the scanner, making the technician having to search for it. This added useless diagnostics time to the general repair charge.

However, it did put in place the basics for what is now a very capable diagnostics and detection system or OBD II. This second generation diagnostics system (1996 and up) is an all encompassing emission fault detection system, and it is always growing and changing as time progresses. The OBD II system will detect faulty areas not only in the engine and transmission, but may also monitor the A/C system, water/coolant thermostat, fuel tank leaks (EVAP system), NOx reducing system or EGR, catalytic converters, oxygen sensors, air injection system, electronic PCV valve, etc.

Late model vehicles (after 2005) are also required to monitor the tire pressure on each tire using a complex pressure detection system. The idea behind the tire pressure monitor is to detect a low pressured tire and issue an alert to the driver so that the problem is corrected. It is estimated that up to 50% of the cars in America drive with low pressure tires, which mean higher fuel consumption.

A low pressure tire will cause the vehicle to use more gas. Multiplied by millions of vehicles on the road today and the expense are in the millions of barrels of oil. In these times of energy problems, every bit counts. The tire pressure monitor is not a futuristic thing; it has been around since the late 1990’s on luxury cars, so plan for it in the future.

A directly related issue regarding the tire pressure monitor to you, the technician, is when it comes to scheduled tire rotation and tire replacement. These newer systems do require a different procedure when rotating the tires. Most of these pressure monitoring systems works by using a built-in transmitter placed inside each tire. Whenever the tire is rotated, the tire pressure module has to be informed of the new location of the rotated tires. All this sounds more difficult than it really is. In most cases, the new tire location can be reprogrammed by placing a special magnet at each tire’s air valve and pressing a couple of buttons on the dash. The important thing is that it has to be done. The other issue is when installing a new tire. Extra care must be taken when replacing the tire so as not to damage the transmitter on the inside of the tire metal rim. Take note that your system is working properly before you have the tires replaced. Each of these transmitters can cost up to $100.

Finally, the tire pressure monitor is not yet part of the OBD II system, but it will be in the very near future. This means that if this system is not working properly, the vehicle will fail a State Inspection test. As you can see, the OBD II system is broad, extensive, and it is also here to stay. The more you know the better prepared that you’ll be. The roots of OBD II dates back to the late 1980’s, when the California Air Resources Board (CARB) wanted to give the average repair shot the resources necessary to properly repair a failing (emission) vehicle.

The OBD II diagnostic system is not really concerned with how well the vehicle is running. This system cares only with whether you’re passing or failing the FTP (Federal Test Procedure) by 1 ½ times or whether you’re polluting the air or not. So, what is the FTP to begin with? The FTP is exactly what is says, a testing procedure instituted by the EPA to determine whether a vehicle is passing an emission test. In actuality, it is based on the conditions present while driving a vehicle through the streets of L.A. The FTP takes into consideration various factors, including the weight of the vehicle.

The passing/failing points are different for every vehicle. This system is also integrated with the ECM’s different modes of operation designed to keep emissions in check in the event of a failure. So for example, it is possible to see a misfiring engine, but NOT TURN the CEL (Check Engine Light) ON. The question then is, why does a misfiring cylinder NOT make the vehicle fail the FTP by 1 ½ times and turn the CEL on? The answer is simple. With today’s faster microprocessors, the ECM has acquired a myriad of features. One of these is the selective injector cut-off.

By simply disabling the injector for the misfiring cylinder, the ECM can maintain the vehicle emissions under the failing point; again this is the OBD II magic value of 1½ times the FTP cutoff value. So, whenever diagnosing an engine performance problem and the vehicle’s CEL is off ask yourself, what is the ECM doing to keep the emissions bellow the failing point (1½ times the FTP)? Just remember that the OBD II diagnostic technician always has to think or act as the vehicle’s ECM does. With proper training and the necessary knowledge, any tech can become proficient at diagnosing OBD II problems.

The various aspects of the OBD II system are always designed with one thing in mind, keep emissions low. The generic OBD II system, as we’ll refer to from now on, is not concerned with how well the vehicle is running. It is only concerned with the emission output of it. Yes, the emission output of a car has a great deal to do with its operation, but nevertheless, it is possible to see a perfectly operational car with excessive emissions. This was the rationale used by the designers of this system. And to a great extent, it is so.

The use of a gas analyzer is many times used by technicians to asses the general operating conditions of a vehicle. We all know that if the O2 level is above 0.50% the mixture tends to be lean or if the CO level is high, there is a rich condition. By the same token, whenever there is a misfire, the HC levels go high as well. The result of unburned gasoline expelled out of the tail pipe. Well, OBD II makes an assertion that if there is a misfire, the HC levels will also go high, or that if the O2 sensor is rich the CO levels will tend to be high as well. This system simply makes the assertions that all technicians make whenever diagnosing a vehicle using the gas analyzer. And, just because an engine is running rich does not mean that it is not passing an emission test.

The converter may be taking up the slack and reducing the excess CO expelled by the engine. OBD II however,